Evaluation of nonaqueous solvents as carrier phases in capillary electrophoresis and capillary electrochromatography

Capillary electrochromatography (CEC) was evaluated as an emerging analytical separation technique. Nonaqueous and unbuffered solvents were investigated for their ability to generate electroosmotic flow (EOF) and were used in new applications for capillary electrokinetic separations.; Nonaqueous solvents and mixed hydro-organic solvents without supporting electrolyte were found to support EOF with flow velocities equivalent to and faster than aqueous buffers traditionally used in capillary separations. Flow reproducibility was good, but equilibration with unbuffered solvents was longer than traditional buffers. Run currents were measured under normal capillary electrokinetic separations conditions and found to be three orders of magnitude lower than traditional aqueous buffers.; Capillary columns were packed in-house and used in a variety of separations. Rugged inlet frits formed from a sol-gel process were used in a pressurized slurry packing procedure. Columns were used in CEC separations and showed efficiencies at and better than the theoretical maximum for liquid chromatography. Separations were run investigating hydrophobic solutes and complex mixtures, while columns of up to 180-{dollar}mu{dollar}m i.d. were packed and used successfully.; Large diameter columns with unbuffered solvents were used to improve detectability for capillary separations. Calibration plots were constructed using open tube columns and concentration limits of detection (LOD) were calculated for several capillary diameters ranging from 50-{dollar}mu{dollar}m to 180-{dollar}mu{dollar}m. Under identical separation conditions, LODs were found to improve exponentially with increasing column diameter due to longer detector cell path length and increased injection volume.; A system allowing on-line injection and gradient elution electrochromatography was developed using a flow injection analysis/capillary electrochromatography interface connected to a micro-HPLC gradient system. Flow through packed columns using the interface was purely electroosmotic in nature. Linear solvent gradient from 50/50 to 100/0 acetonitrile/water were produced using the interface. Test solutes were run in both isocratic and gradient modes, with gradient separations showing improved peak shape, resolution and decreased analysis time. Design of the interface prolonged column lifetime from days to weeks and was compatible with an autoinjector for routine analysis.